5.2 染色体和基因
Section outline
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Identical Twins, Identical Genes
::同同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同、同You probably can tell by their close resemblance that these two fancy ladies are identical twins. Identical twins develop from the same fertilized egg , so they inherit copies of the same and have all the same genes . Unless you have an identical twin, no one else in the world has exactly the same genes as you. What are genes? How are they related to chromosomes? And how do genes make you the person you are? Let's find out!
::你也许能从他们的近似中看出这两个美女是相同的双胞胎。同性双胞胎是从同一个受精蛋中发育出来的,所以他们继承了同一个双胞胎的复制件,并拥有所有相同的基因。除非你有一个相同的双胞胎,否则世界上没有其他人拥有与你完全相同的基因。什么是基因?它们与染色体有何关系?基因如何使你成为真正的人?我们来看看!Introducing Chromosomes and Genes
::介绍染色体和基因Chromosomes are coiled structures made of and . They are encoded with genetic instructions for making and proteins. These instructions are organized into units called genes . There may be hundreds (or even thousands!) of genes on a single chromosome. Genes are segments of DNA that code for particular pieces of RNA. Once formed, some RNA molecules go on to act as blueprints for building proteins, while other RNA molecules help regulate various processes inside the . S ome regions of DNA do not code for RNA and serve a regulatory function, or have no known function .
::染色体由循环结构组成,并被编码成基因指令和蛋白质。这些指令分为基因单位。在单一染色体上可能存在数百个基因(甚至数千个!),基因是DNA中用来编码RNA特定片段的部分。一旦形成,一些RNA分子就继续作为构建蛋白质的蓝图,而其他RNA分子则帮助规范了该物质内部的各种过程。有些DNA区域不为RNA编码,而是发挥一种调控功能,或者没有已知功能。Human Chromosomes
::人类染色体Each is characterized by a set number of chromosomes. The human number is 23. Humans cells normally have two sets of chromosomes in each of their cells, one set inherited from each parent. Because chromosomes occur in pairs, these cells are called diploid or 2N. There are 23 chromosomes in each set, for a total of 46 chromosomes per diploid cell. Each chromosome in one set is matched by a chromosome of the same type in the other set, so there are 23 pairs of chromosomes per cell. Each pair consists of chromo somes of the same size and shape, and they also contain the same genes. The chromosomes in a pair are known as homologous chromosomes .
::每个染色体都有一组染色体的特征。 人数是23。 人类细胞每组通常有两组染色体, 每组由母体继承一组。 由于染色体是双对的, 这些细胞称为二N。 每组中共有23个染色体, 每组中共有46个染色体。 每组中每组染色体与另一组中同类的染色体相匹配, 因此每组中各有23对染色体。 每组染色体由相同大小和形状的染色体组成, 它们也包含相同的基因。 一组中的染色体被称为同质染色体。All human cells (except gametes, which are sperm and egg cells) have the 23 pairs of chromosomes shown here.
::所有人类细胞(除调子外,是精子和蛋细胞)均在此显示23对染色体。Autosomes
::自动Of the 23 pairs of human chromosomes, 22 pairs are called autosomes (numbers 1–22 in the figure ). Autosomes are chromosomes that contain genes for characteristics that are unrelated to sex. These chromosomes are the same in males and females. The great majority of human genes are located on autosomes.
::在23对人类染色体中,有22对被称为异体体(图1至22)。 异体是染色体,含有与性别无关特性的基因。 这些染色体在男性和女性中是相同的。 绝大多数人类基因都位于异体上。Sex Chromosomes
::性染色体The remaining pair of human chromosomes consists of the sex chromosomes , X and Y. Females have two X chromosomes, and males have one X and one Y chromosome . In females, one of the X chromosomes in each cell is inactivated and known as a Barr body. This ensures that females, like males, have only one functioning copy of the X chromosome in each cell.
::其余的一对人类染色体由性染色体、X和Y组成。 女性有2个X染色体,男性有1个X和1个Y染色体。在女性中,每个细胞中的1个X染色体没有活性,被称为巴尔身体。这确保了女性与男性一样,每个细胞中只有1个X染色体的功能副本。As you can see from the figure above, the X chromosome is much larger than the Y chromosome. The X chromosome has about two thousand genes, whereas the Y chromosome has fewer than 100, none of which is essential to survival. Virtually all of the X chromosome genes are unrelated to sex. Only the Y chromosome contains genes that determine sex. A single Y chromosome gene, called SRY (which stands for sex-determining region Y gene), triggers an embryo to develop into a male. Without a Y chromosome, an individual develops into a female, so you can think of female as the default sex of the human species.
::从上图中可以看出,X染色体比Y染色体大得多。X染色体有大约2 000个基因,而Y染色体只有不到100个基因,而Y染色体没有生存所必需的任何基因。几乎所有的X染色体基因都与性无关。只有Y染色体含有决定性别的基因。单一的Y染色体基因,称为SRY(代表性别-确定区域Y基因),触发一个胚胎发展成一个男性。没有Y染色体,一个人就会发展成一个女性,这样你就可以将女性视为人类的默认性别。Human Genes
::人类基因Humans have an estimated 20 thousand to 22 thousand genes. This may sound like a lot, but it really isn’t. Far simpler species have almost as many genes as humans. However, human cells use splicing and other processes to make multiple proteins from the instructions encoded in a single gene. Only about 25 percent of the nitrogen base pairs of DNA in human chromosomes make up genes and their regulatory elements . The functions of many of the other base pairs are still unclear.
::人类的基因估计有2万到2万2千个。这听起来可能听起来像很多,但确实不是。 更简单的物种的基因几乎和人类一样多。 然而,人类细胞使用切片和其他过程从单基因编码的指示中制造多种蛋白质。 人类染色体中只有大约25%的氮基DNA配对组成基因及其调控元素。 其他许多基本对的功能还不清楚。The majority of human genes have two or more possible versions, called . Differences in alleles account for the considerable among people. In fact, most human genetic variation is the result of differences in individual DNA base pairs within alleles.
::大部分人类基因有两种或两种以上可能的版本,称为 。 异性之间差异是人与人之间相当多的原因。 事实上,大多数人类基因变异是异性之间个体DNA基对差异的结果。Linkage
::链接Genes that are located on the same chromosome are called linked genes . Linkage explains why certain characteristics are frequently inherited together. For example, genes for hair color and eye color are linked, so certain hair and eye colors tend to be inherited together, such as blonde hair with blue and brown hair with brown eyes. Can you think of other human traits that seem to occur together? Do you think they might be controlled by linked genes?
::位于同一染色体上的基因被称为关联基因。 链接解释了为什么某些特征经常被一起继承。 比如, 头发颜色和眼睛颜色的基因是相连的, 所以某些头发和眼睛的颜色往往是一起继承的, 比如金发和蓝色头发, 棕色头发和棕色眼睛的金发。 你能想到其他似乎同时发生的人类特征吗? 你认为它们可能受关联基因的控制吗?Genes located on the sex chromosomes are called sex-linked genes . Most sex-linked genes are on the X chromosome, because the Y chromosome has relatively few genes. Strictly speaking, genes on the X chromosome are X-linked genes , but the term sex-linked is often used to refer to them. The diagram below is called a linkage map . A linkage map shows the locations of specific genes on a chromosome. The linkage map shows the locations of a few of the genes on the human X chromosome.
::存在于性染色体上的基因称为与性有关的基因。大多数与性有关的基因都存在于X染色体上,因为Y染色体的基因相对较少。严格地说,X染色体上的基因是X相连基因,但性联系的术语常常用来指它们。下面的图表称为连接图。连接图显示染色体上的具体基因的位置。联系图显示人类X染色体上少数基因的位置。Linkage Map for the Human X Chromosome. This linkage map shows the locations of several genes on the X chromosome. Some of the genes code for normal proteins. Others code for abnormal proteins that lead to genetic disorders.
::人类 X 染色体链接图 。 此链接图显示 X 染色体上几个基因的位置 。 一些正常蛋白质的基因代码 。 其他导致基因紊乱的异常蛋白质代码 。Summary
::摘要-
Chromosomes are coiled structures made of DNA and proteins that are encoded with genetic instructions for making RNA and proteins. The instructions are organized into units called genes
, which are
segments
of DNA that code for particular pieces of RNA. The RNA molecules can then act as a blueprint for proteins, or directly help regulate various cellular processes.
::染色体由DNA和蛋白质组成,并配有用于制作RNA和蛋白质的基因指令。这些指令被组织成称为基因的单位,这些单位是DNA的部位,对RNA的具体部分进行编码。 RNA分子可以作为蛋白质的蓝图,或者直接帮助调节各种细胞过程。 -
Each species is characterized by a set number of chromosomes. The normal chromosome complement of a human cell is 23 pairs of chromosomes. Of these, 22 pairs are autosomes, which contain genes for characteristics unrelated to sex. The other pair consists of sex chromosomes (XX in females, XY in males). Only the Y chromosome contains genes that determine sex.
::每个物种都有一组染色体的特征,人类细胞的正常染色体补充体为23对染色体,其中22对是异体,含有与性别无关的基因,另一对是性染色体(女性为XX,男性为XY)。只有Y染色体含有决定性别的基因。 -
Humans have an estimated 20 thousand to 22 thousand genes. The majority of human genes have two or more possible versions, which are called alleles.
::人类估计有2万至2万2千个基因,大多数人类基因有两种或两种以上可能的基因,称为异形基因。 -
Genes that are located on the same chromosome are called linked genes. Linkage explains why certain characteristics are frequently inherited together. A linkage map shows the locations of specific genes on a chromosome.
::位于同一染色体上的基因被称为连接基因。链接解释了为什么某些特性经常被一起继承。链接图显示染色体上的具体基因的位置。
Review
::回顾1. What are chromosomes and genes? How are the two related?
::1.什么是染色体和基因?这两种染色体和基因之间有何关联?2. Describe human chromosomes and genes.
::2. 描述人类染色体和基因。3. Explain the difference between autosomes and sex chromosomes.
::3. 解释异体与性染色体之间的区别。4. What are linked genes, and what does a linkage map show?
::4. 什么是关联基因,联系图显示什么?5. Explain why females are considered the default sex in humans.
::5. 解释为什么女性被视为人类的默认性行为。6. True or False: Humans have 46 pairs of chromosomes.
::6. 真实或假:人类有46对染色体。7. True or False: Autosomes refer to any chromosome other than sex chromosomes.
::7. 真实或假:体外体是指除性染色体以外的任何染色体。8. True or False: The majority of human DNA does not encode for proteins.
::8. 真实或假:大多数人类DNA没有蛋白质编码。9. Explain the relationship between genes and alleles.
::9. 解释基因和异形之间的关系。10. Put the following in order of size, from smallest to largest:
::10. 以下按大小排列,从最小到最大:chromosome; gene; base pair
::染色体;基因;基对11. In which chromosome are sex-linked genes usually found? Explain why these genes are called "sex-linked."
::11. 哪些染色体是通常发现的与性别有关的基因?解释为什么这些基因被称为“与性别有关的基因”。12.Which of the following are considered homologous chromosomes?
::12. 以下哪些是同族染色体?a. chromosome 22 and the X chromosome
::a. 染色体22和X染色体b. the two copies of chromosome 22 that make up a pair
::b. 构成一对的22种染色体的两份c. all of the chromosomes in a skin cell and all of the chromosomes in a muscle cell
::c. 皮肤细胞中的所有染色体和肌肉细胞中的所有染色体d. chromosomes 21 and 22
::d. 染色体21和2212. What is the one chromosome that is different between genetic males and females? Explain your answer.
::12. 男女遗传基因之间有哪些不同的染色体?解释一下答案。13. Most males and females have two sex chromosomes. Why do only females have Barr bodies?
::13. 大多数男性和女性有两种性染色体,为什么只有女性才有巴尔身体?Explore More
::探索更多Watch the video below to learn about noncoding DNA.
::观看下面的视频 学习关于非编码DNA。Watch the video below to learn about sex chromosomal disorders, such as Turner syndrome.
::了解性染色体紊乱, 例如特纳综合症。 -
Chromosomes are coiled structures made of DNA and proteins that are encoded with genetic instructions for making RNA and proteins. The instructions are organized into units called genes
, which are
segments
of DNA that code for particular pieces of RNA. The RNA molecules can then act as a blueprint for proteins, or directly help regulate various cellular processes.
